docs: def ecdsa_signature_normalize(self, raw_sig, check_only=False):
          """
          Check and optionally convert a signature to a normalized lower-S form.
          If check_only is True then the normalized signature is not returned.
  
          This function always return a tuple containing a boolean (True if
          not previously normalized or False if signature was already
          normalized), and the normalized signature. When check_only is True,
          the normalized signature returned is always None.
          """
          if check_only:
              sigout = ffi.NULL
          else:
              sigout = ffi.new('secp256k1_ecdsa_signature *')
  
          result = lib.secp256k1_ecdsa_signature_normalize(
              self.ctx, sigout, raw_sig)
  
          return (bool(result), sigout if sigout != ffi.NULL else None)